Comet P/2016 j1 (panstarrs)

R. Weryk and R. Wainscoat reported the discovered of an apparent comet in four w-band exposures obtained with the 1.8-m Pan-STARRS1 telescope at Haleakala on May 5.5 UT (discovery observations tabulated below), with evidence in the stacked image of a very short tail extending towards the west for approximately 2"; the FWHM of adjacent stars varies between 1".0 and 1".3 in the four images, while this object has a FWHM of approximately 1".5 in a stacked image.

2016 UT R.A. (2000) Decl. Mag.

May 5.46342 15 46 25.09 - 6 48 03.9 21.4

5.47541 15 46 24.62 - 6 47 57.1 21.5

5.48743 15 46 24.14 - 6 47 49.8 21.4

5.49944 15 46 23.66 - 6 47 43.1 21.3

Three 60-s follow-up images obtained by Wainscoat (queue observer D. Woodworth) at the 3.6-m Canada-France-Hawaii Telescope (+ w-band filter) atop Mauna Kea on May 6.43 showed a second comet in the field; the images of both comets were measured by M. Micheli, the astrometry of the second comet being tabulated below.

2016 UT R.A. (2000) Decl. Mag. Observer

May 6.42589 15 45 56.31 - 6 38 47.7 21.6 Wainscoat

6.42716 15 45 56.26 - 6 38 47.0 21.8 "

7.44503 15 45 17.04 - 6 29 04.0 21.5 "

7.44700 15 45 16.96 - 6 29 03.0 21.4 "

7.44897 15 45 16.88 - 6 29 01.8 21.4 "

Micheli notes that the two components are moving at nearly identical rates in nearly identical directions (both about 0".6/minute in p.a. about 314 deg). The brighter component (designated component A) displays a clear and quite thin tail about 10" long in p.a. 250 deg in the May 6.43 images. The fainter object (designated component B) also displays a clear but broader tail of similar length, oriented toward p.a. about 210 deg. Micheli adds that a series of three 120-s exposures obtained with the CFHT on May 7.4 by Wainscoat and Woodworth confirm the two objects with basically the same morphologies as seen in the previous day's images.

After the brighter component was posted on the Minor Planet Center' PCCP webpage, other CCD astrometrists of also noted the cometary appearance of component A. H. Sato, Tokyo, Japan, reports that twenty-four stacked 60-s exposures taken with a 0.43-m f/6.8 astrograph (+ luminance filter) near Mayhill, NM, USA, on May 6.3 UT show component A to be strongly condensed with a round coma 8" in diameter; the total w-band magnitude was 20.8 as measured within a circular aperture of radius 5".7. V-band images taken by W. H. Ryan and E. V. Ryan with the Magdalena Ridge Observatory 2.4-m f/8.9 reflector on May 8.35-8.39 show a tail in p.a. about 250 deg.

The available astrometry for both components and ephemerides appear on MPEC 2016-J90. The following preliminary orbital elements by G. V. Williams for component A are from 24 observations spanning May 5-8:

T = 2016 Aug. 25.5715 TT Peri. = 68.2929

e = 0.254080 Node = 197.8881 2000.0

q = 2.326552 AU Incl. = 13.4483

a = 3.119035 AU n = 0.1789261 P = 5.51 years

Very preliminary elements for component B are based on those for component A, with T and Peri. modified:

T = 2016 Aug. 25.2149 TT Peri. = 68.2069

e = 0.254080 Node = 197.8881 2000.0

q = 2.326552 AU Incl. = 13.4483

a = 3.119035 AU n = 0.1789261 P = 5.51 years